Thin film magnetic recording disks typically comprise a substrate, such as an aluminum-magnesium (AlMg) alloy with a nickel-phosphorous (NiP) surface coating. The NiP is covered with a magnetic film, typically either a cobalt based metal alloy or a gamma phase iron oxide film. The magnetic film can be covered with a protective overcoat such as a sputter deposited amorphous carbon or a hydrogenated carbon film. A general description of the structure of such thin film disks is illustrated in U.S. Pat. Nos. 4,610,911 to Opfer, et al., and 4,552,820 to Lin, et al. A thin film disk having an amorphous carbon film as an overcoat is illustrated in U.S. Pat. No. 4,503,125 to Nelson, et al., and a thin film disk having a hydrogenated carbon film as an overcoat is described in U.S. Pat. No. 4,778,582 to Howard.
Data is recorded onto a magnetic disk having the structure described above by a read/write head. The read/write head is placed close to the surface of the magnetic disk which rotates at a high rate of speed. When the disk is rotating at a high rate of speed, the read/write head is lifted off the disk by air pressure from the rotating disk. When the disk is starting, stopping, or not rotating fast enough, the read/write head slides along the disk surface. A liquid lubricant, such as a fluoroether lubricant, is added to the surface of the carbon based protective overcoat to prevent damage to the magnetic disk, when the read/write head slides on the disk. Alternatively, the lubricant could be placed directly on the magnetic film without the use of an overcoat. The magnetic film may or may not have undergone any post processing after deposition. The lubricant prevents damage to the disk by reducing the friction between the read/write head and the disk.
Liquid lubrication of the disk surface has at least two problems which limit its effectiveness as used in rotating storage media. First, the lubricant does not have a retention means so that when the disk rotates, the lubricant spins off the disk. The depletion of the lubricant thickness from the disk surface increases the friction between the disk and the read/write head. Second, the depletion of the thickness of the lubricant is not uniform across the surface of the disk. Where the thickness is too thin, the head can cause wear on the disk surface. Where the lubricant thickness is too great, the head will become stuck in the lubricant (from static friction) and the head or disk could be damaged when the head suddenly becomes unstuck due to the rotating disk. Other failure modes include the inability of the spindle motor to start at all due to the static friction and failure of the mechanical suspension assembly. These effects are present even though the depletion is radial in nature.
One way in which to bond the lubricant to the disk and therefore prevent the depletion has been to thermally bond the lubricant to the disk surface. This technique increases the exposure of the magnetic media to corrosion and degrades the reliability of the disk. Another technique is to use a process having high energy electron beams. The lubricant is exposed to electron beams having an energy above ten KeV. This process has been shown to produce a modified lubricant film bonded to the disk surface. However, the modified film does not contain all the required lubricating properties of the unmodified film.
It is the object of this invention to bond a lubricating film onto the surface of a thin film storage media without encountering the prior art limitations. In particular the bonding process must bond a thick enough and uniform enough film to the storage media to prevent wear while avoiding problems associated with static friction. In addition the process must not degrade the chemical stability of the film bonded to the surface to minimize storage media corrosion. Finally, the process must bond a variety of lubricants to the storage media. The lubricants bonded must not be limited to polymers having a reactive end group.